Former South Korean President Yoon Suk Yeol returned to jail on Thursday after a court approved a warrant sought by prosecutors investigating his attempt to impose martial law last year.

The Seoul Central District Court’s decision bolstered the special counsel investigation into allegations that Yoon’s move in December represented obstruction of justice and abuse of power.

The court said in a statement it granted the request because of concerns Yoon could seek to destroy evidence.

The conservative politician already faces criminal charges of insurrection over his martial law decree, and that could carry a sentence of life in prison or death.

The former president returned to confinement in the Seoul Detention Center about 20 km (12 miles) south of the capital after the decision. He spent 52 days in jail earlier in the year but was released four months ago on technical grounds.

The Constitutional Court ousted him as president in April, upholding parliament’s impeachment for the martial law bid, which shocked South Koreans and triggered months of political turmoil.

The special prosecution team launched its investigation after new leader Lee Jae Myung was elected in June, and it has been looking into additional charges against Yoon.

The special counsel team is now expected to speed up its probe into allegations, including whether Yoon hurt South Korea’s interests by intentionally inflaming tensions with North Korea.

Yoon attended the court hearing on Wednesday on the detention warrant, wearing a dark navy suit and a red tie, but did not answer questions from reporters.

His lawyers have denied the allegations against him and called the detention request an unreasonable move in a hasty investigation.

More than 1,000 supporters rallied near the court on Wednesday, local media reported, waving flags and signs and chanting Yoon’s name in heat of 35 degrees Celsius (95 degrees Fahrenheit).

In their warrant request, prosecutors said Yoon poses a flight risk, local media reported.